Magnetoresistive sensor including magnetic domain control layers having high electric resistivity, magnetic head and magnetic disk apparatus

ABSTRACT

There are provided a magnetoresistive sensor of the type of flowing a signal sensing current perpendicular to the plane to improve resolution at reproducing a signal, a magnetic head using the magnetoresistive sensor, and a magnetic disk apparatus.  
     A magnetoresistive sensor comprising a substrate, a pair of magnetic shield layers consisting of a lower magnetic shield layer and an upper magnetic shield layer, a magnetoresistive sensor layer, disposed between the pair of magnetic shield layers, an electrode terminal for flowing a signal current perpendicular to the plane of the magnetoresistive sensor layer, and magnetic domain control layers for controlling Barkhausen noise of the magnetoresistive sensor layer, wherein the magnetic domain control layers disposed in contact with opposite ends of the magnetoresistive sensor layer consist of a material having high electric resistivity and with a specific resistance not less than 10 mΩcm so as to give the magnetoresistive sensor having excellent reproducing resolution. The sensor is used to provide a magnetic head having excellent reproducing resolution and a magnetic disk apparatus.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a magnetoresistive sensorincluding magnetic domain control layers for the magnetoresistive sensorfor reading back magnetically recorded information, a magnetic head, anda magnetic disk apparatus. More specifically, it relates to amagnetoresistive sensor having excellent reproducing resolution, amagnetic head using the same, and a magnetic disk apparatus.

[0003] 2. Description of the Related Art

[0004] The recording density in a magnetic disk apparatus has beenimproved significantly, and the demand that the performance of themagnetic read/write heads thereof be enhanced is increased in regard toboth characteristics of read and write.

[0005] Regarding the read head sensor, it is necessary to improve thetechniques concerning three points: (1) improvement of a technique formaking the efficiency higher, (2) improvement of a technique for makingthe track width smaller, and (3) a technique for making the gap betweenthe write magnetic shields smaller.

[0006] With respect to (1), making the efficiency higher has beenadvanced by developing an MR head utilizing a magnetoresistive effect.At a low recording density of several giga bits per square inch(Gb/in2), anisotropic magnetoresistive effect (AMR) is used to convertthe magnetic signal on recording media to an electric signal. At a highrecording density exceeding this, a higher efficient giantmagnetoresistive effect (GMR) is used to respond to this high recordingdensity. However, when making the efficiency much higher is advanced,the structure must be changed to the perpendicular magnetic recordingstructure in relation to the read element, which makes the most of GMR(CPP-GMR) or a tunnel magnetoresistive effect (TMR) of a system forflowing a sensing current perpendicular to the plane.

[0007] As a known example of a magnetic head employing GMR, JapanesePatent Publication No. Hei 8(96)-21166 (Japanese Un-examined PatentPublication No. Hei 4(92)-358310) describes the structure called a spinvalve. This comprises a pinned layer consisting of a magnetic materialin which a anti-ferromagnetic layer pins magnetization in the specificdirection, and a free layer consisting of a non-magnetic thin filmlaminated on the pinned layer and a magnetic layer laminated through thenon-magnetic thin film, so as to change electric resistance at arelative angle of magnetization of the pinned layer and the free layer.

[0008] With respect to (2), the track width is made smaller to improvethe track density. It is generally thought that the read track width isdetermined by the distance between electrodes flowing a sensing currentfor sensing changed resistance. The read sensor has a high loss of S/Nwhen Barkhausen noise is caused, and it is necessary to control this.The Barkhausen noise is caused together with microscopic domain wallmovement, and there must be arranged magnetic domain control layers soas to provide the read sensor singly in the form of a magnetic domain.The magnetic domain control layers are often arranged on opposite sidesof the sensor layer portion of the read sensor, viewed from themedia-opposed surface side. The magnetic domain control layer isgenerally a hard magnetic metal material layer formed on a suitablemetal underlayer, and an insulating oxide layer is required for thecontact surface of the same with the magnetoresistive sensor layer, thetop surface of the lower shield, and the contact surface of the samewith the upper shield. The magnetic domain control layer provides amagnetic field for the magnetoresistive sensor layer, so that theanisotropic magnetic field is increased effectively and the exteriormagnetic efficiency is reduced greatly. For this reason, JapaneseUn-examined Patent Publication No. Hei 9(97)-282618 describes thestructure in which the gap between the electrodes is smaller, than thatbetween the magnetic domain control layers, and a sensor region havingan efficiency effective for the exterior magnetic field is used forsensing a signal.

[0009] With respect to (3) the technique for making the read gapsmaller, that is, for making the gap between the read magnetic shieldssmaller, there has been studied improvement of linear recording densityby modifying resolution. Generally, the shield layers are arranged atthe upper and lower sides so as to interpose the magnetoresistive sensorlayer, and a gap layer made of an insulating material is disposedbetween the shield layer and the magnetoresistive sensor layer so as toprevent a sensing current from being leaked to the shield. When the gapbetween the read magnetic shields is smaller, the thickness of the gaplayer is reduced. Thus, the thickness dependence as the characteristicof the insulating layer or the presence of pinhole cannot maintain theinsulating properties, so that an electric current for sensing a signal(sensing current) is leaked to the magnetic shield to reduce readoutput. This loss is called a shunting loss.

[0010] As a method of solving this, Japanese Un-examined PatentPublication No. Hei 5(93)-266437 describes the structure in which aninsulating magnetic layer is arranged on the surface of themagnetoresistive sensor layer side of at least one of the magneticshields.

[0011] The read element is difficult to provide a sufficient recordingmagnetic field in a conventional in-plane magnetic recording system.Further, CPP (Current Perpendicular to the Plane)-GMR or TMR as a highefficient magnetoresistive sensor is a magnetoresistive sensor utilizinga structure flowing a sensing current perpendicular to the plane. Thus,a future structure of the read element is thought to be of the CPPsystem employing a sensing current. However, employing such a structure,when the area of the magnetoresistive sensor layer is reduced, therearises a new problem that the conventional magnetic domain control layeris difficult to ensure the insulating properties of the magnetic domaincontrol layer. In other words, the conventional magnetic domain controllayer is arranged on the lower magnetic shield by employing a laminatingstructure of insulating layer/(metal underlayer)/hard magnetic metalmaterial layer/insulating layer, and then is in contact with oppositeends of the magnetoresistive sensor layer. The magnetoresistive sensorlayer is made thinner and finer; there are imposed three problems: (1)the throwing power of the lower insulating layer is insufficient so asto shunt the sensing current flowing to the magnetoresistive sensorlayer to the magnetic domain control layer, resulting in reduction ofoutput, (2) the thick lower insulating layer is adhered so as toincrease the gap between the magnetoresistive sensor layer and themagnetic domain control layer, thereby making the magnetic domaincontrol different from the design, and (3) in consideration of thethickness maintaining the pressure resistance of the insulating layer,the magnetic layer thickness of the magnetic domain control layer isreduced relatively, so as not to ensure a predetermined susceptibility,thereby making it difficult to design the magnetic domain control.Further, when employing the yoke structure or the flux guide structureof the TMR element, these must be magnetic domain controlled. Simply,there is employed means for laminating a plurality of theabove-mentioned magnetic domain control layer. This will involve a verydifficult problem in process.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide amagnetoresistive sensor having, in particular, excellent reproducingresolution, in magnetic read and write, a magnetic head using the same,and a magnetic disk apparatus, and, for that, to provide magnetic domaincontrol layers having high electric-resistivity suitable for improvingthe reproducing resolution of the magnetoresistive sensor.

[0013] In order to achieve the foregoing objects, the present inventionsolves the above-mentioned problems with respect to the magnetic domaincontrol layer by the following means, and provides a magnetoresistivesensor having excellent reproducing resolution, a magnetic head usingthe same, and a magnetic disk apparatus.

[0014] Conventionally, the magnetic domain control layer is arranged onthe lower magnetic shield by employing a multi-layered structure ofinsulating layer/(metal underlayer)/hard magnetic metal materiallayer/insulating layer. In the present invention, there is used meanswherein the magnetic domain control layer comprises a single layer madeof a hard magnetic material having high electric resistivity, therebydirectly performing magnetic domain control. According to this method,the insulating layers arranged at the upper and lower sides of themagnetic layer can be omitted. Thus, when the magnetoresistive sensorlayer is made thinner, a loss of the susceptibility due to the thicknessof the insulating layer can be reduced, so as to lower the shunting lossof an electric current. In addition, since the magnetic domain controllayer is in direct contact with the magnetoresistive sensor layer, theloss of the magnetic field of the magnetic domain control can beminimized.

[0015] As a hard magnetic material having high electric resistivity withsuch characteristics, there are (1) a magnetic oxide having a spinellattice, and (2) a granular magnetic material made of a hard magneticmetal material and a non-magnetic insulating material. With respect to(1), there is γ-Fe2O3 or the like. When a γ-Fe2O3 (004) layer grows, theresidual magnetization is relatively large, the coercivity is high, andthe specific resistance is high and 10⁵ to 10⁶Ωcm. Thus, this isadaptable to the above-mentioned single magnetic domain control layer.As for such a system, there is also γ-(FeCo)2O4.

[0016] However, in order to exhibit the magnetic characteristic bymaking the spinel lattice thinner, it is generally necessary tomanufacture the layer at a very high substrate temperature (above 500°C). When the layer is manufactured in a practical temperature rangebelow 300° C. using a sputtering method, it tends to be an amorphouslayer. As means of solving this, there is envisaged a method ofinserting one high orientation thin oxide film or one single crystalthin film, with an NaCl structure, under the spinel lattice magneticlayer, so as to form thereon the above-mentioned magnetic domain controllayer having high electric resistivity, and this is used as means.

[0017] Examples of the underlayer material for use in this methodinclude CoO (200), MgO (200), NiO (200), EuO (200), FeO (200) and ZnO(001). These materials can be relatively easily grown at roomtemperature by means of the sputtering method. When a spinel typecompound γ-Fe2O3 is grown on this plane, it is found that the γ-Fe2O3(400) plane can be manufactured on these oxides in a relatively lowtemperature range below 300° C. These thin oxide films can exhibit afunction as the underlayer even in the thickness range of 1 nm to 5 nm.These underlayers are electrically an insulator to insulatingsemiconductor. Basically, they can eliminate shunting from themagnetoresistive sensor layer to the magnetic domain control layer.

[0018] In the granular magnetic material made of a hard magnetic metalmaterial and a non-magnetic insulating material, the multi-layerlaminated is formed using the mixed sputtering method or the sputteringmethod, so that a hard magnetic material in granular form is formed inthe non-magnetic insulating material. At this time, when the granularvolume is smaller than the critical volume (granular volume V in whichthermal energy kT is larger than magnetic energy MV+KV), the materialbecomes magnetically paramagnetic, or weak soft magnetic. However, whenthe granular particle is larger than the critical volume and thegranular shape is changed anisotropically for pinning by the insulator,it can become magnetically hard. The granular magnetic material of thepresent invention is a material in which the hard magnetic metalmaterial is enclosed by the non-magnetic insulating material, and thegranular volume is larger than the critical volume. When theabove-mentioned conditions are met, the granular shape is optional.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a diagram showing the sectional structure of themedia-opposed surface side of the magnetoresistive sensor of Example 1of the present invention and the position of a magnetic domain controllayer;

[0020]FIG. 2 is a cross-sectional view of the depth direction of themagnetoresistive sensor of Example 1 of the present invention;

[0021]FIG. 3 is a cross-sectional view of the media-opposed surface sideof Example 1 (3) of the present invention showing the position relationbetween the magnetic domain control layer having high electricresistivity and the magnetoresistive sensor layer;

[0022]FIG. 4 is a cross-sectional view of the media-opposed surface sideof Example 1 (2) of the present invention showing the position relationbetween the magnetic domain control layer having high electricresistivity and the magnetoresistive sensor layer;

[0023]FIG. 5 is a cross-sectional view of the media-opposed surface sideof Example 1 (1) of the present invention showing the position relationbetween the magnetic domain control layer having high electricresistivity and the magnetoresistive sensor layer;

[0024]FIG. 6 is a cross-sectional view of the media-opposed surface sideof Example 1 (4) of the present invention showing the position relationbetween the magnetic domain control layer having high electricresistivity and the magnetoresistive sensor layer;

[0025]FIG. 7 is a cross-sectional view of the media-opposed surface sideof Example 4 of the present invention showing the position relationbetween the magnetic domain control layer having high electricresistivity and the magnetoresistive sensor layer;

[0026]FIG. 8 is a diagram showing the sectional structure of themedia-opposed surface side of the magnetoresistive sensor of Example 5of the present invention and the position of the magnetic domain controllayer;

[0027]FIG. 9 is a cross-sectional view of the depth direction of themagnetoresistive sensor of Example 5 of the present invention;

[0028]FIG. 10 is a three-dimensional block diagram showing the structureof the exposed type magnetoresistive sensor of Examples 1 and 5 of thepresent invention;

[0029]FIG. 11 is a block diagram schematically showing one example ofthe yoke structure shown in Example 5 of the present invention and theposition of the magnetic domain control layers of the present inventionto magnetic domain-control this;

[0030]FIG. 12 is one example of the position of the magnetic domaincontrol layers of the yoke structure shown in Example 5 of the presentinvention;

[0031]FIG. 13 is one example of the position of the magnetic domaincontrol layers of the yoke structure shown in Example 5 of the presentinvention;

[0032]FIG. 14 is a block diagram schematically showing one example ofthe flux guide type yoke structure shown in Example 5 of the presentinvention and one example of the position of the magnetic domain controllayers of the present invention to magnetic domain-control this;

[0033]FIG. 15 is a diagram showing one example of the shape of the fluxguide type yoke of Example 5 of the present invention, and one exampleof the position relation between the same and the magnetoresistivesensor;

[0034]FIG. 16 is a diagram showing one example of the shape of the fluxguide type yoke of Example 5 of the present invention, and one exampleof the position relation between the same and the magnetoresistivesensor layer;

[0035]FIG. 17 is one example of the position of the magnetic domaincontrol layers of the yoke structure shown in Example 5 of the presentinvention;

[0036]FIG. 18 is one example of the position of the magnetic domaincontrol layers of the yoke structure shown in Example 5 of the presentinvention;

[0037]FIG. 19 is a schematic diagram of the structure and operation of amagnetic disk apparatus of Example 6 of the present invention;

[0038]FIG. 20 is a side view of one example of the structure of MRAMusing the magnetoresistive sensor layer provided with the magneticdomain control layers having high electric resistivity of the presentinvention;

[0039]FIG. 21 is a diagram of FIG. 20 viewed perpendicular to thesubstrate surface (representing state “1”); and

[0040]FIG. 22 is a diagram in which the direction of an electric currentflowing through the conductive line is shifted 90 degrees from that ofFIG. 21 (representing state “0”).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Embodiments of the present invention will be described based onthe examples with reference to the drawings.

Example 1

[0042]FIGS. 1 and 2 are diagrams showing the structure of amagnetoresistive sensor as one embodiment according to the presentinvention viewed from the media-opposed surface and section of the planeperpendicular to the depth direction, respectively. Arrow 110 in thedrawing denotes the depth direction.

[0043] On a substrate 101 is formed a base insulating layer 102, madeof, for example, alumina. After subjected to precision polishing bymeans of chemimechanical polishing (CMP), a lower magnetic shield layer103 is formed thereon. This is made of Ni81Fe19 having a thickness of 2μm manufactured by, for example, the sputtering method, the ion beamsputtering method, or the plating method. A resist mask is patterned ina predetermined size in this layer, and other portions thereof aresubjected to ion milling to strip off the resist. Al2O3 is grown thereonto fill in portions 104 removed by ion milling. After this is subjectedto CMP, an electrode layer made of Cu or Ru (not shown) is grown by 20nm, so as to form a drawing electrode layer 111 in a portion away fromthe sensor portion. This is, for example, a layer made of Ta, Au and Ta.

[0044] A lift-off pattern is formed in a region on the previouselectrode layer consisting of a magnetoresistive sensor layer, so as toform thereon a layer having a thickness of 150 nm made of a mixture ofAl2O3 and SiO2. This may be a single phase layer made of Al2O3 or SiO2.After lifting this off, a magnetoresistive sensor layer 105 is formed.In the magnetoresistive sensor layer, there are studied as the examplestwo types of using GMR and of using TMR. An electric current for sensinga signal (sensing current) is flowed perpendicular to the plane of thesemagnetoresistive sensor layers (Current Perpendicular to the Plane: CPP)

[0045] A GMR layer comprises, for example, from the lower side, aCo48Mn52 anti-ferromagnetic layer of 12 nm, a pinned layer consisting ofCo of 1 nm, Ru of 0.8 nm and Co of 2 nm, a free layer consisting of Cuof 2 nm, Co of 0.5 nm and Ni81Fe19 of 2.5 nm, and Ta of 3 nm. Withrespect to the anti-ferromagnetic layer, in the case of using a regularanti-ferromagnetic layer of a PtMn system, anneal is required in orderto exhibit the exchange bonding between the pinned layer and theanti-ferromagnetic layer. The magnetic field of the pinned layer isdirected in the in-plane direction orthogonal to the depth.

[0046] On the other hand, a TMR layer comprises, for example, from thelower side, a free layer consisting of Ta of 5 nm, NiFe of 3 nm and aCoFe layer of 2 nm, a barrier layer consisting of Al2O3 of 2 nm, apinned layer consisting of CoFe of 2 nm, Ru of 1 nm and CoFe of 1 nm, aanti-ferromagnetic layer consisting of MnIr of 10 nm, Ta of 3 nm, andNiFe of 5 nm.

[0047] After forming the magnetoresistive sensor layer 105, a lift-offmaterial is formed in the position as an active region (on the layerserved both as the lower shield and electrode). Then, themagnetoresistive sensor layer is etched, for example, by the ion millingmethod. After etching, magnetic domain control layers 106 are formed soas to remove the lift-off mask. Thereafter, a pattern in the depthdirection of the magnetoresistive sensor layer 105 is formed in themagnetic domain control layers 106, and then, the portion therearound isremoved by the ion milling. A mixed layer of Al2O3 and SiO2 having athickness of 150 nm is formed thereon as a protective insulating layer107 to define an upper shield layer 112.

[0048] A write element having a magnetic core laminated through arecording gap is formed on the magnetoresistive sensor to define amagnetic head of the magnetic disk apparatus.

[0049] By means of a method represented by the above-mentionedmanufacture method, the magnetoresistive sensor of the present inventionand the magnetic head using the same are manufactured. In this, themagnetic domain control layer 106 has a required characteristicdifferent from the case of flowing an electric current in the plane. Inthe magnetic domain control layer, there have been studied the magneticdomain control layer itself is: (1) a layer made by laminating, from thelower portion, an insulating layer Al2O3-SiO2 layer of 220 nm, a Crunderlayer of 5 nm, a magnetic layer CoCrPt of 25 nm, and an insulatingprotective Al2O3-SiO2 layer of 220 nm on the top, (2) a layer made bylaminating, as the magnetic layer, a CoO underlayer of 5 nm, and aγ-Fe2O3 layer of 50 nm, (3) a layer made by laminating, as the magneticlayer, a γ-Fe2O3 layer of 50 nm, and (4) a layer by alternatelylaminating CoCrPt of 1.5 nm and SiO2 of 1.1 nm (60 nm thick).

[0050] In the method (1), there is shown a conventional magnetic domaincontrol layer as shown in the schematic structure of FIG. 5, as acomparative example. When the conventional magnetic domain control layeris applied as-is, the gap between the shields Gs not less than 70 nmmakes it possible to manufacture magnetic domain control layers 501, 502and 503. However, the following points in formation of the junction ofthe ends of the magnetoresistive sensor layer are important in order tomaintain insulation of the CoCrPt (502) from the lower portion Al2O3(501).

[0051] One of the points is that, in order to maintain insulation, theends of the magnetoresistive sensor layer 105 must be completely coatedby the Al2O3 layer 501, the hard metal magnetic CoCrPt (502) must begrown thereon, and the Al2O3 layer 503 grown thereon must completelycoat the CoCrPt layer. For this reason, the sputtering apparatus formingthe layer needs to have a characteristic such that the Al2O3 is insertedinto the lift-off pattern in the plane, and CoCrPt is not inserteddeeply therein, and to ensure such manufacture conditions. Further, formanufacture, the lift-off pattern must be formed, and when the size ofthe sensor is reduced (not more than 1 μm), the formation thereof isdifficult. The insulating layer having a thickness less than 20 nmcannot have sufficient insulation properties, and when the layer isthick in order to maintain the sufficient insulation properties, the gapbetween the end of the magnetoresistive sensor layer 105 and the CoCrPtlayer as the magnetic domain control layer is larger, so that themagnetic domain control force is weak, thereby making magnetic domaincontrol impossible. For this reason, when the gap between the shields isnot more than 70 nm in order to make the resolution of the read headhigh, the method (1) is difficult to use.

[0052] The method (2) is one embodiment of the present invention shownin FIG. 4. First, a lower shield 302 is formed on an appropriatelytreated substrate 301, and the region in contact with opposite ends ofthe magnetoresistive sensor layer 105 thereon is formed with a CoOunderlayers 304. CoO (002) is grown in the CoO underlayer, and γ-Fe2O3(65 nm) is formed thereon, so as to manufacture a magnetic domaincontrol layer 303. γ-Fe2O3 has a (004) orientation plane by the effectof the underlayer. This is the same for Co-γ-Fe2O3 as other ferrite.

[0053] This layer has a specific resistance not less than several 10 Ωcmin the layer state. In this case, the layer requires no lift-offpattern, and can be manufactured by the usual resist pattern. Themagnetoresistive sensor layer may be in contact with the magnetic domaincontrol layer, or the magnetic domain control layer may be lifted on themagnetoresistive sensor layer. According to this method, the magneticdomain control layer has electric resistivity much higher than themagnetoresistive sensor layer. A signal sensing current flows onlythrough the magnetoresistive sensor layer, so as to eliminate a loss ofthe signal intensity due to shunting to the magnetic domain controllayer.

[0054] Even when the gap between the shields is smaller, the insulatingprotective layer of conventional type is unnecessary. According to this,it is possible to reduce the total thickness of the magnetic domaincontrol layer causing an equivalent susceptibility. The susceptibilityis an amount to determine the thickness of the magnetic domain controllayer by multiplying the magnetization of the free layer of themagnetoresistive sensor layer by the thickness thereof. In the case ofthe magnetic domain control layer, multiplication of the residualmagnetization by the thickness is equivalent to this. γ-Fe2O3 orCo-γ-Fe2O3 in this study has a high specific resistance of 10⁵ to 10⁶Ωcm, a coercivity of about 1.3 to 5.0 kOe, a residual magnetization of1.2 to 3.5 kG, and a saturated magnetization of 3.5 to 4.2 kG. Thesevalues are smaller than those of CoCrPt (having a coercivity of about1.0 to 3.0 kOe, a residual magnetization of 4 to 9 kG, and a saturatedmagnetization of 6.5 to 12.0 kG). In consideration of the protectiveinsulating layer, it is effective for the magnetic domain control whenthe gap between the shields is small. As the layer formation process,the conventional four layers (Al2O3/Cr/CoCrPt/Al2O3) can be reduced totwo layers, so as to make the operation efficient.

[0055] In the method (3) as another example of the present invention,FIG. 3 shows a basic construction. This is the same as the method (2)except that the oxide underlayer 304 of the magnetic domain controllayer is absent. In view of the manufacture method, the point ofdirectly forming γ-Fe2O3 is different. In this case, the substratetemperature is raised to 300 to 500° C., and then, the layer is formedby the high vacuum layer forming apparatus having a maximum degree ofvacuum of 10⁻¹¹ Torr, or the top surface of the lower shield exposed isirradiated with an oxygen ion using an ECR ion source to oxidize thesurface, so that γ-Fe2O3 can be precedably grown. In this case, the sameeffect as in the method (2) is found to be given.

[0056] The method (4) as another example of the present invention hasthe structure of FIG. 6. A magnetic domain control layer 601 in thiscase is a layer by alternately laminating CoCrPt of 1.5 nm and SiO2 of1.1 nm. The thickness ratio of CoCrPt/SiO2 is between 2:1 and 1:2,CoCrPt has a layer thickness of 0.5 to 2 nm, a specific resistance notless than 10 mΩcm, a coercivity not more than about 1.0 kOe, and aresidual magnetization of 2 to 4 kG, so as to give the same effect asdescribed above. However, in this case, it is more effective that Al2O3not less than 10 nm is inserted for the underlayer.

[0057] In the methods (2) to (4) of this example, even when the gapbetween the read shields (gap distance) is not more than 70 nm, the readcharacteristic is not found to be deteriorated due to the conduction ofthe magnetoresistive sensor layer and the magnetic domain control layer.

Example 2

[0058] The magnetoresistive sensor in Example (1) described above hasthe structure by lamination from the lower portion. The structure inwhich the upper and lower portions are reversed can also give the sameeffect.

Example 3

[0059] In Example (1) described above, in formation of the magneticdomain control layer using a spinel type oxide such as γ-Fe2O3, on theunderlayer 304 of the magnetic domain control layer 303, is formed, inplace of the CoO layer, an oxide layer having a crystal structure ofNaCl type such as Mg (200), NiO (200), EuO (200), FeO (200) or ZnO (200)as well as a (200) plane. Then, the spinel ferrite formed thereon can becrystallized at low temperature. As a method of forming this layer,there is a method of manufacturing these layers by the sputteringmethod, the ion beam sputtering method or the cluster ion beam method.As a method other than this, on the lower shied 302 a layer of Co, Mg,Ni, Eu, Fe or Zn is formed in a thickness of 1-5 nm. This layer isexposed to oxygen in vacuum, is irradiated with oxygen using ECR plasma,or is exposed to low-pressure oxygen by heating the substrate (100 to250° C.) so as to form an oxide layer, thereby forming a spinel ferritethereon. This method can give equivalent results.

[0060] As a spinel type oxide formed on the oxide underlayer 304, thereare γ-Fe2O3 and Co-γ-Fe2O3. The latter is thought to be a solid solutionof γ-Fe2O3 and CoFe2O3, and is represented by the chemical formula(Co(y)Fe(8-2y)/3)O4(γ-Fe2O3). The ratio of Co is varied to change thecoercivity. As compared with the case that these are formed on a glasssubstrate, a high coercivity increased 1.5 to 2 times is exhibited inthe same thickness as that of these formed on the oxide underlayer, andwhen the Co/Fe ratio is 0.08, a coercivity of 2.6 kOe in 10 nm.

Example 4

[0061] Before forming the magnetic domain control layer of Example 1(1), as shown in FIG. 7, portions 701 are formed with MnZn ferrite as asoft magnetic layer having high electric resistivity, an insulator and ametal magnetic material are alternately laminated, or there is formed agranular layer in which these are sputtered at the same time into amixed state, for example, a layer by laminating, by 25 number of layers,Co90Fe10 layers having a thickness of 1.4 nm and Al2O3 layers having athickness of 1.0 nm. Thereafter, the outside of the layer is removed bythe ion milling in the position several mm away from the outerperipheral portion of the magnetoresistive sensor layer, and then metalmagnetic layers such as CoCrPt as represented by 502 are formed in theremoved portions. This structure has no shunting since the metalmagnetic domain control layers 502 are not in direct contact with themagnetoresistive sensor layer. However, since a layer with soft magneticproperties is disposed therebetween, the magnetic field of the magneticdomain control is effectively applied to the magnetoresistive sensorlayer.

Example 5

[0062] In the magnetoresistive sensor with the magnetoresistive sensorlayer is exposed, according to a three-dimensional schematic diagramexploding the structure of the magnetoresistive sensor, as shown in FIG.10, the magnetic domain control layers 106 are arranged on opposite endsof the magnetoresistive sensor layer 105, and the magnetic shields 103and 109 are disposed at the upper and lower sides thereof. In thepresent invention described in the above examples, the layer 106 is amaterial having high electric resistivity. There is a magnetoresistivesensor of another structure, that is, a magnetoresistive sensor providedwith a yoke structure as the write sensor. FIG. 11 is athree-dimensional diagram schematically showing a representative yokestructure and the magnetic domain control layer. In this structure, amagnetoresistive sensor layer 1105 is not exposed from the surfaceopposite the media. In the gap between a lower magnetic shield 1103 andan upper magnetic shield 1107, made of Ni81Fe19, are arranged yokelayers made of a similar soft magnetic material. The properties of thisstructure described below are observed. In FIG. 11, the yoke layers in Cring form consist of an upper yoke 1106 joined to a lower yoke 1102.Other than this, the lower yoke is reduced on the end thereof, or has athick film, or the yoke is discontinuous under the magnetoresistivesensor layer. In the diagram, a magnetic domain control layer 1101 isshown. The magnetic domain control layer having high electricresistivity shown in Example 1 of the present invention is used as thelayer. This magnetic domain-controls at least the lower yoke and themagnetoresistive sensor layer and has no shunting in the periphery. Themagnetic domain control layer has a type for magnetic domain-controllingthe upper and lower yoke layers and the magnetoresistive sensor layer atthe same time, and a type for magnetic domain-controlling each. Ineither structure, it is found that the good magnetic domain control ispossible without shunting.

[0063] The above-mentioned FIG. 11 is a block diagram for simply showingthe position of the magnetic domain control layer in the yoke structure.In detail, the magnetic domain control layer is manufactured in astructure of the magnetoresistive sensor layer as one example of thepresent invention viewed from the media-opposed surface and a structurerepresented by the diagram showing a section of the depth direction, asshown in FIGS. 8 and 9.

[0064]FIG. 14 shows a schematic diagram of the flux guide type yokestructure and the magnetic domain control thereof. The surface viewedfrom the XY side in the diagram is the media-opposed surface. On themagnetoresistive sensor layer disposed on the lower shield 1002 so as tobe recessed, is formed a soft magnetic layer made of, for example,Ni89Fe19, as indicated by 1401, having a shape, which extends from theposition exposed from the media-opposed surface onto themagnetoresistive sensor layer, is in contact with the surface oppositethe media-opposed surface of the magnetoresistive sensor layer, andextends to a depth direction Z. This layer guides the magnetic flux fromthe recording media to the magnetoresistive sensor layer, and is calleda flux guide. In order to magnetic domain-control this flux guide layer,in the process of forming the magnetoresistive sensor layer, ionmilling, patterning, forming the flux guide layer 1401, and forming themagnetic domain control layer 1001, the magnetic domain control materialhaving high electric resistivity of the present invention is used as themagnetic domain control layer 1001 to give the following advantages.Conventionally, the insulating protective layer must be formed in thetrack width direction of the magnetoresistive sensor layer. In thepresent invention, even when the magnetic domain control layer is formeddirectly, magnetic domain control is possible without shunting. In theflux guide type yoke structure, it is also possible to magneticdomain-control the magnetoresistive sensor layer together with the fluxguide type yoke.

[0065] As shown in FIGS. 15 and 16, in order to increase an amount ofthe magnetic flux sensed by the magnetoresistive sensor layer, theportion in contact with the magnetoresistive sensor layer of the yoke isdiscontinuous. In such a structure, the material of the magnetic domaincontrol layer is a layer having high electric resistivity so as to formthe magnetic domain control layer of the present invention. Examples ofarrangement of the magnetic domain control layer of the yoke structureof this embodiment are shown in FIGS. 17 and 18.

Example 6

[0066]FIG. 19 is a diagram showing the magnetic disk apparatus of oneembodiment using the magnetic head mounting the magnetoresistive sensoraccording to the present invention.

[0067] The magnetic disk apparatus illustrated comprises a magnetic disk1901 as a magnetic recording media formed in disk form for recordingdata in a recording region called a concentric track and a magnetictransducer, a magnetic head 1906 comprising a magnetic transducer,reading and writing the data and mounting the magnetoresistive sensoraccording to the present invention (in detail, comprising a magnetichead 1910 and a slider 1909), actuator means 1911 for supporting themagnetic head 1906 to move it to a predetermined position on themagnetic disk 1901, and control means for controlling transmission andreceive of data by read and written by the magnetic head and movement ofthe actuator means.

[0068] The structure and operation will be described below. At least onerotatable magnetic disk 1901 is supported by a rotation axis 1902, andis rotated by the drive motor 1903. At least one slider 1909 is placedon the magnetic disk 1901, one or more sliders 1909 are disposed, andsupport the magnetic head 1910 according to the present invention forread and write.

[0069] The magnetic disk 1901 is rotated, and at the same time, themagnetic head 1906 is moved on the disk surface for access to apredetermined position in which data to be desired are recorded. Themagnetic head 1906 is provided on an arm 1908 by a gimbal 1907. Thegimbal 1907 has slight elasticity and brings the magnetic head 1906 intocontact with the magnetic disk 1901. The arm 1908 is mounted on theactuator 1911.

[0070] There is a voice coil motor (hereinafter referred to as VCM) asthe actuator 1911. VCM consists of a movable coil placed in the magneticfield fixed, and the movement direction and movement speed of the coilare controlled by an electric signal given from the control means 1912through a line 1904. The actuator means of this embodiment comprises,for example, the magnetic head 1906, the gimbal 1907, the arm 1908, theactuator 1911 and the line 1904.

[0071] During operation of the magnetic disk, the magnetic disk 1101 isrotated to cause air bearing due to air flow between the magnetic head1906 and the disk surface, which lifts the magnetic head 1906 from thesurface of the magnetic disk 1901. During operation of the magnetic diskapparatus, the air bearing is balanced with the slight elasticity of thegimbal 1907, the magnetic head 1906 is not in contact with the magneticdisk surface, and is maintained so as to be lifted from the magneticdisk 1901 at a constant interval.

[0072] The control means 1912 generally comprises a logic circuit,memory, and microprocessor. The control means 1912 transmits andreceives a control signal through each line, and controls variousstructure means of the magnetic disk apparatus. For example, the motor1903 is controlled by a motor driven signal transmitted through the line1904.

[0073] The actuator 1911 is controlled so as to optimally move andposition, by means of a head position control signal and a seek controlsignal through the line 1904, the magnetic head 1906 selected to a datatrack to be desired on the magnetic disk 1901 associated therewith.

[0074] The magnetic head 1910 reads data on the magnetic disk 1901 so asto convert the data to an electric signal. The control signal receivesand decodes the electric signal through the line 1904. In addition, anelectric signal written as data to the magnetic disk 1901 is transmittedthrough the line 1904 to the magnetic head 1910. In other words, thecontrol means 1912 controls transmission and receive of information reador written by the magnetic head 1910.

[0075] The read and write signals described above permit means directlytransmitted from the magnetic head 1910. There are, for example, anaccess control signal and a clock signal as the control signal. Themagnetic disk apparatus may have a plurality of magnetic disks andactuators, and the actuator may have a plurality of magnetic heads.

[0076] Such plurality of mechanisms are provided, so as to form theso-called disk array apparatus.

[0077] In this apparatus, the magnetoresistive sensor of the presentinvention is used as the magnetoresistive sensor of the magnetic head.It is thus possible to improve reproducing resolution of the apparatusaccording to improved performance of the magnetoresistive sensor.

Example 7

[0078]FIG. 20 shows a representative structure of an already known MRAMas one example of the magnetic recording sensor. The magnetic recordingsensor has a structure comprising a plurality of cells in parallelincluding a magnetoresistive sensor layer 2002 for recordinginformation, a bit line 2001 connected to the magnetoresistive sensorlayer for flowing an electric current to the sensor, a word line 2005 inthe position opposite the bit line 2001 by interposing therebetween themagnetoresistive sensor layer 2002 and in the position away from themagnetoresistive sensor layer 2002 for performing recording operationonto the magnetoresistive sensor layer orthogonally to the bit line, anamplifying system for amplifying a read signal, and a read conductiveline 2007 for switching between read and write, wherein themagnetoresistive sensor layer 2002 comprises the magnetoresistive sensorlayer as shown in Example 1. Since an electric current flowsperpendicular to the plane, the use of the magnetoresistive sensor layeris similar to that of Example 1. The magnetoresistive sensor layer hasthe size consisting of one side of 0.2 to 0.25 μm. The magnetization ofthe free layer of the magnetoresistive sensor layer is rotated in thedirection of an electric current flowing through the word line and thebit line, by varying the direction of the synthetic magnetic fieldcaused in the magnetoresistive sensor layer portion. When themagnetization direction of the free layer of the magnetoresistive sensorlayer is rotated and the magnetic domain is caused in the free layer,the resistance value to the magnetic field is varied to lower the S/Nratio, so that memory cannot be read. In order to controllably performthis, the magnetic domain control layer is required. Magnetic domaincontrol layers having high electric resistivity 2008 devised in thepresent invention are positioned on opposite ends of themagnetoresistive element layer 2002. Thus, magnetic domain control ispossible without loss of shunting to the magnetic domain control layer,so as to improve the recording density of the magnetic recording sensor.

[0079] According to the present invention, in the magnetoresistivesensor using the magnetoresistive sensor layer, (1) a loss of shuntingto the magnetic domain control layer can be eliminated, (2) the numberof conventional processes for manufacturing the magnetic domain controllayer can be reduced, and (3) magnetic domain control can be conductedfinely by making the gap between the shields smaller since the thicknessof the magnetic domain control layer can be reduced by the size of thepressure-resistant protective layer. Accordingly, (4) themagnetoresistive sensor flowing an electric current perpendicular to theplane can provide the magnetic domain control layer practicable.Further, the magnetoresistive sensor of the present invention is used toprovide the magnetic head having excellent reproducing resolution andthe magnetic disk apparatus.

What is claimed is:
 1. A magnetoresistive sensor including a substrate,a pair of magnetic shield layers consisting of a lower magnetic shieldlayer and an upper magnetic shield layer, a magnetoresistive sensorlayer disposed between the pair of magnetic shields, an electrodeterminal for flowing a signal current perpendicular to the plane of themagnetoresistive sensor layer, and magnetic domain control layers forcontrolling Barkhausen noise of said magnetoresistive sensor layer,wherein said magnetic domain control layers disposed on opposite ends ofthe magnetoresistive sensor layer in a region from the end surface of amedia-opposed surface side of the magnetoresistive sensor layer to thedepth position are made of a material having a specific resistance notless than 10 mΩcm, and are in contact with at least opposite endsurfaces of said magnetoresistive sensor layer in said region.
 2. Themagnetoresistive sensor according to claim 1, comprising magnetic yokelayers disposed between the pair of magnetic shields, having a shapeextended from the position exposed from the media-opposed surface in thedepth direction, and guiding the magnetic field of the recording mediato its interior, wherein said magnetoresistive sensor layer is disposedbetween the magnetic yoke layers in the position recessed from themedia-opposed surface, said magnetic domain control layers are providedon opposite ends of the magnetoresistive sensor layer in a region fromthe end surface of the media-opposed surface side of themagnetoresistive sensor layer and the magnetic yoke layer to the depthposition and are in contact with at least opposite end surfaces of saidmagnetoresistive sensor layer in said region, and the magnetic domaincontrol layers are in contact with opposite end surfaces of saidmagnetic yoke layer in at least one portion of the region from the endsurface of the media-opposed surface side of said magnetic yoke layer tothe depth position.
 3. The magnetoresistive sensor according to claim 1,comprising a flux guide type magnetic yoke layer disposed between thepair of magnetic shields, having a shape extended from the positionexposed from the media-opposed surface in the depth position, and beingin contact with any one of the magnetic shield layers to guide themagnetic flux of the media, and magnetic domain control layers forcontrolling Barkhausen noise of the magnetoresistive sensor layer andthe flux guide type magnetic yoke layer, wherein said magnetoresistivesensor layer is disposed at the upper or lower side of said flux guidetype yoke layer in the position recessed from the media-opposed surface,the flux guide type yoke layer has an discontinuous portion in a regionin contact with said magnetoresistive sensor layer, said magnetic domaincontrol layers disposed on opposite ends of the magnetoresistive sensorlayer in the region from the end surface of the media-opposed surfaceside of said magnetoresistive sensor layer and said flux guide typemagnetic yoke layer to the depth position are in contact with at leastopposite end surfaces of said magnetoresistive sensor layer in theregion from the end surface of the media-opposed surface side of saidmagnetoresistive sensor layer to the depth position, and the magneticdomain control layers are in contact with opposite end surfaces of saidmagnetic yoke layer in at least one portion of the region from the endsurface of media-opposed surface side of said magnetic yoke layer to thedepth position.
 4. The magnetoresistive sensor according to claim 1,wherein said magnetic domain control layer is made of an underlayer madeof an oxide having a thickness not more than 5 nm, and an oxide materialhaving high electric resistivity not less than 10 mΩcm formed on theoxide underlayer.
 5. The magnetoresistive sensor according to claim 2,wherein said magnetic domain control layer is made of an underlayer madeof an oxide having a thickness not more than 5 nm, and an oxide materialhaving high electric resistivity not less than 10 mΩcm formed on theoxide underlayer.
 6. The magnetoresistive sensor according to claim 3,wherein said magnetic domain control layer is made of an underlayer madeof an oxide having a thickness not more than 5 nm, and an oxide materialhaving high electric resistivity not less than 10 mΩcm formed on theoxide underlayer.
 7. A magnetoresistive sensor including a substrate, apair of magnetic shield layers consisting of a lower magnetic shieldlayer and an upper magnetic shield layer, a magnetoresistive sensorlayer disposed between the pair of magnetic shields, an electrodeterminal for flowing a signal current perpendicular to the plane of themagnetoresistive sensor layer, and magnetic domain control layers forcontrolling Barkhausen noise of said magnetoresistive sensor layer,wherein a material consisting of said magnetic domain control layersdisposed on opposite ends of the magnetoresistive sensor layer in theregion from the end surface of the media-opposed surface side of themagnetoresistive sensor layer to the depth position is a compound havinga composition of R2O3 containing at least R (R=Fe, Co, Mn, and Ni) andoxygen (O) and has a spinel lattice and a (400) orientation plane, andthe magnetic domain control layers are in contact with at least oppositeend surfaces of said magnetoresistive sensor layer in said region. 8.The magnetoresistive sensor according to claim 7, comprising magneticyoke layers disposed between the pair of magnetic shields, having ashape extended from the position exposed from the media-opposed surfacein the depth direction, and guiding the magnetic field of the recordingmedia to its interior, wherein said magnetoresistive sensor layer isdisposed between the magnetic yoke layers in the position recessed fromthe media-opposed surface, materials consisting of said magnetic domaincontrol layers disposed on opposite ends of the magnetoresistive sensorlayer in the region from the end surface of the media-opposed surfaceside of the magnetoresistive sensor layer and the magnetic yoke layer tothe depth position are in contact with at least opposite end surfaces ofsaid magnetoresistive sensor layer in the region from the end surface ofthe media-opposed surface side of the magnetoresistive sensor layer tothe depth position, and the magnetic domain control layers are incontact with opposite end surfaces of said magnetic yoke layer in atleast one portion of the region from the end surface of themedia-opposed surface side of said magnetic yoke layer to the depthposition.
 9. The magnetoresistive sensor according to claim 7,comprising a flux guide type magnetic yoke layer disposed between thepair of magnetic shields, having a shape extended from the positionexposed from the media-opposed surface in the depth position, and beingin contact with any one of the magnetic shield layers to guide themagnetic flux of the media, and magnetic domain control layers forcontrolling Barkhausen noise of the magnetoresistive sensor layer andthe flux guide type magnetic yoke layer, wherein said magnetoresistivesensor layer is disposed at the upper or lower side of said flux guidetype yoke layer in the position recessed from the media-opposed surface,the flux guide type yoke layer has an discontinuous portion in theregion in contact with said magnetoresistive sensor layer, said magneticdomain control layers disposed on opposite ends of the magnetoresistivesensor layer in the region from the end surface of the media-opposedsurface side of said magnetoresistive sensor layer and said flux guidetype magnetic yoke layer to the depth position are in contact with atleast opposite end surfaces of said magnetoresistive sensor layer in theregion from the end surface of the media-opposed surface side of saidmagnetoresistive sensor layer to the depth position, and the magneticdomain control layers are in contact with opposite end surfaces of saidmagnetic yoke layer in at least one portion of the region from the endsurface of media-opposed surface side of said magnetic yoke layer to thedepth position.
 10. The magnetoresistive sensor according to claim 7,wherein a material consisting of the oxide underlayer of said magneticdomain control layer is a compound of RO consisting of at least R(R=Co,Mg, Ni, Eu, Fe, and Zn) and oxygen (O) and has a NaCl structure and a(200) orientation plane, and a material consisting of said magneticdomain control layer on the oxide underlayer is a compound having acomposition of R2O3 containing at least R (R=Fe, Co, Mn, and Ni) andoxygen (O) and has a spinel lattice and a (400) orientation plane. 11.The magnetoresistive sensor according to claim 8, wherein a materialconsisting of the oxide underlayer of said magnetic domain control layeris a compound of RO consisting of at least R(R=Co, Mg, Ni, Eu, Fe, andZn) and oxygen (O) and has a NaCl structure and a (200) orientationplane, and a material consisting of said magnetic domain control layeron the oxide underlayer is a compound having a composition of R2O3containing at least R (R=Fe, Co, Mn, and Ni) and oxygen (O) and has aspinel lattice and a (400) orientation plane.
 12. The magnetoresistivesensor according to claim 9, wherein a material consisting of the oxideunderlayer of said magnetic domain control layer is a compound of ROconsisting of at least R(R=Co, Mg, Ni, Eu, Fe, and Zn) and oxygen (O)and has a NaCl structure and a (200) orientation plane, and a materialconsisting of said magnetic domain control layer on the oxide underlayeris a compound having a composition of R2O3 containing at least R (R=Fe,Co, Mn, and Ni) and oxygen (O) and has a spinel lattice and a (400)orientation plane.
 13. The magnetoresistive sensor according to claim 7,wherein a material consisting of said magnetic domain control layer is agranular layer made by mixing a hard magnetic material having highcoercivity made of a metal magnetic material having as the compositionelements Co (cobalt), Cr (chromium), Pt (platinum), Ta (tantalum), andNb (niobate) with an insulating material made of Al2O3, SiO2, HfO2,TaO2, TiO2, Ta2O5, AlN, AlSiN, or ZrO2.
 14. The magnetoresistive sensoraccording to claim 7, wherein said magnetic domain control layercomprises a layer made of a soft magnetic oxide material having highelectric resistivity disposed in contact with opposite ends of saidmagnetoresistive sensor layer, and a hard magnetic layer, disposedoutside the same, made of a metal magnetic material having as thecomposition elements Co (cobalt), Cr (chromium), Pt (platinum), Ta(tantalum), and Ni (niobate).
 15. The magnetoresistive sensor accordingto claim 1, wherein said magnetic domain control layer is at leastpartially superimposed on the plane of said magnetoresistive sensorlayer.
 16. The magnetoresistive sensor according to claim 1, whereinsaid magnetoresistive sensor layer is a tunnel magnetoresistive sensorlayer.
 17. A combined magnetic head mounting a write element and a readelement, wherein the read element comprises the magnetoresistive sensoraccording to claim
 1. 18. A magnetic disk apparatus, comprising amagnetic recording media for recording information, a magneticread/write head having a write sensor for recording information ontosaid magnetic recording media and a read sensor for detectinginformation recorded onto said magnetic recording media, a read/writecircuit for transmitting and receiving a read signal from and a writesignal to said read/write head, an actuator for moving said read/writehead to a predetermined position on said magnetic recording media, andmeans for controlling the read/write operation controlling saidread/write circuit and actuator, wherein said read head comprises themagnetoresistive sensor according to claim
 1. 19. A magnetic recordingsensor having a structure comprising a plurality of cells in parallelincluding a magnetoresistive sensor for recording information, a bitline connected to the magnetoresistive sensor for flowing an electriccurrent to the sensor, a word line in the position opposite the bit lineby interposing therebetween the magnetoresistive sensor layer and in theposition away from the magnetoresistive sensor layer for performingrecording operation onto the magnetoresistive sensor layer orthogonallyto the bit line, an amplifying system for amplifying a read signal, anda read word line for switching between read and write, wherein themagnetoresistive sensor comprises the magnetoresistive sensor layer, anda layer for magnetic domain-controlling the magnetoresistive sensorlayer is provided with the magnetic domain control layer having highelectric resistivity according to any one of claims 1.